Qt: Use Roboto for cover placeholder text

Consistency across platforms.

src/duckstation-qt/gamelistwidget.cpp

@@ -333,6 +333,7 @@ void GameListModel::createPlaceholderImage(QImage& image, const QImage& placehol
   {
     QFont font;
     font.setPixelSize(std::max(static_cast<int>(64.0f * scale), 1));
+    font.setFamilies(QtHost::GetRobotoFontFamilies());
     painter.setFont(font);
 
     const int margin = static_cast<int>(30.0f * scale);

src/duckstation-qt/qthost.cpp

@@ -141,6 +141,8 @@ struct State
   std::unique_ptr<QTimer> settings_save_timer;
   std::vector<QTranslator*> translators;
   QLocale app_locale;
+  std::once_flag roboto_font_once_flag;
+  QStringList roboto_font_families;
   bool batch_mode = false;
   bool nogui_mode = false;
   bool start_fullscreen_ui = false;
@@ -2731,6 +2733,28 @@ std::string QtHost::GetResourcePath(std::string_view filename, bool allow_overri
                           Path::Combine(EmuFolders::Resources, filename);
 }
 
+const QStringList& QtHost::GetRobotoFontFamilies()
+{
+  std::call_once(s_state.roboto_font_once_flag, []() {
+    const int font_id = QFontDatabase::addApplicationFont(
+      QString::fromStdString(Path::Combine(EmuFolders::Resources, "fonts/Roboto-VariableFont_wdth,wght.ttf")));
+    if (font_id < 0)
+    {
+      ERROR_LOG("Failed to load Roboto font.");
+      return;
+    }
+
+    s_state.roboto_font_families = QFontDatabase::applicationFontFamilies(font_id);
+    if (s_state.roboto_font_families.isEmpty())
+    {
+      ERROR_LOG("Failed to get Roboto font family.");
+      return;
+    }
+  });
+
+  return s_state.roboto_font_families;
+}
+
 bool Host::ResourceFileExists(std::string_view filename, bool allow_override)
 {
   const std::string path = QtHost::GetResourcePath(filename, allow_override);

src/duckstation-qt/qthost.h

@@ -379,6 +379,9 @@ QString GetResourcesBasePath();
 /// Returns the path to the specified resource.
 std::string GetResourcePath(std::string_view name, bool allow_override);
 
+/// Returns the font family for the bundled Roboto font.
+const QStringList& GetRobotoFontFamilies();
+
 /// Returns the base settings interface. Should lock before manipulating.
 INISettingsInterface* GetBaseSettingsInterface();